"Treetop Trail" Lets Philadelphia Zoo Primates Go Exploring

Forget the old way of building a zoo. The Philadelphia Zoo just opened a new system of elevated steel mesh trails that lets monkeys and lemurs explore the environment around themand human visitors to get a closer look at primates.

Forget the old way of building a zoo, where animals are cloistered in cages. The Philadelphia Zoo just opened a new system of elevated steel mesh trails that lets monkeys and lemurs explore the environment around them—and human visitors to get a closer look at primates.

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Venturing Out

Venturing Out

In most zoos, it's the human visitors who get to travel freely, exploring the different areas and exhibits while the animals stay confined to their living spaces. At the Philadelphia Zoo, that old-fashioned approach is starting to change. A new project called the Treetop Trail, which opened July 28, is an experiment in the way a zoo is set up, allowing primates to venture out from their home.

Philadelphia Zoo

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The Trail

The Trail

The trail is network of more than 700 feet of tunnels made of flexible stainless-steel mesh, with steel rings installed every few feet to support the weight of the monkeys and the mesh. Treetop Trail's design, construction and modifications cost a total of $1.5 million, which was partially funded by a number of partnerships, but it is the realization of a long-held vision to get animals out of their dens and moving around.

Venturing Out

In most zoos, it's the human visitors who get to travel freely, exploring the different areas and exhibits while the animals stay confined to their living spaces. At the Philadelphia Zoo, that old-fashioned approach is starting to change. A new project called the Treetop Trail, which opened July 28, is an experiment in the way a zoo is set up, allowing primates to venture out from their home.

Philadelphia Zoo

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The Trail

The trail is network of more than 700 feet of tunnels made of flexible stainless-steel mesh, with steel rings installed every few feet to support the weight of the monkeys and the mesh. Treetop Trail's design, construction and modifications cost a total of $1.5 million, which was partially funded by a number of partnerships, but it is the realization of a long-held vision to get animals out of their dens and moving around.

Around the Plaza

"The animals live in the building on one side of the plaza, and they get out the top and back of the building into the transportation trail system," zoo CEO Andy Baker says. "That allows them to go around to the front of the building through the ring of trees on the other side of the plaza."

Philadelphia Zoo

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Oasis

Each species will have its own opportunity to explore the trails, with a specified time during the week to traverse the system without interference from any other species. Baker says that this time-sharing helps avoid fights between these territorial species, and it also reveals their differences. "It's entirely voluntary, and so each species is going to decide if, when and how much of this they want to use," Baker says. "As we've begun giving species the opportunity, some have been very quick to take advantage of it, and others are going to take their time and just explore and get used to it much more slowly." Along the path, there are little oases like the one seen here, where the steel and mesh open up and encapsulate the trees that support them, providing enough space for primates to meet.

Most of the primates move about independently and return to their home, where they're comfortable, before their time allotted on the trail elapses. But, Baker says, the primate specialists also keep a supply of the animals' favorite foods as an enticement to go home, just in case the primates stay out past their curfew.

Philadelphia Zoo

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Up Close

Because the network of passageways is made of mesh, human visitors to the zoo can watch the monkeys explore rather than simply look at the primates as they hang around in a building. Humans can't get too close, though: "We always maintain a distance of six feet between our visitors and our primates," Baker says. "That's the closest that people are getting at any point." And don't worry about any of the primates escaping, he adds. It's not as though chimps or gorillas will be traveling the trails; the small monkeys and lemurs allowed in the tunnels aren't strong enough to pull the stainless steel apart.

Of course, having monkeys crawling through elevated mesh tunnels brings up another question. To put it bluntly, what about the danger of falling feces?

"Where [the trail] crosses over the visitor path, of course we're worried about visitors staying free of debris and so on, so there is a solid sort of structure that visitors walk under," Baker says. "It defines an entrance to the plaza but also protects from anything that might be falling from the trail system overhead."